Understanding the factors that impact on drug abuse treatment is important in designing effective treatments strategies and treatment programs for drug abusers. The effects of concurrent comorbid mental disorders (particularly alcoholism, major depression and antisocial personality disorder) have been previously studied, but many questions remain unanswered. A longitudinal study is proposed of 936 patients (50% female) with cocaine, heroin and/or alcohol use disorders treated in drug, alcohol and psychiatric facilities. The index evaluations for one- third of the sample will have been completed as part of another study. Patient's current and past histories of substance use, substance use disorders, and psychiatric disorders (including PTSD) will be ascertained at baseline, as well as drug and alcohol use, family history, treatment history and functioning in a number of areas. Patients will then be seen for four follow-up interviews at six-month intervals (two years total), and systematically evaluated by trained clinical interviewers on the course of their substance use, substances use disorders, psychiatric conditions and treatment status since the last evaluation. Procedures will be implemented throughout the study to maintain accurate assessment and a high follow-up rate. Information will be collected on changes in substance abuse status (remission and relapse), psychiatric status, and treatment status, and (as closely as possible) the specific points in time when changes in these statue have occurred. Data will be recorded in a manner suitable for survival analysis. With some proposed development of statistical methods and software, the powerful methods of survival analyses will be used to investigate remission and relapse of substance use disorders, as well as changes in dependence status throughout the two years of follow-up. The use of time-dependent covariates offer the advantage of being able to examine the effects of changes in psychiatric and treatment status when they change during the follow-up period methods also allow investigation of the stability of dependence (number of previous changes in dependence status during the follow-up) on subsequent course. The proposal includes a plan to develop comparisons of the effects of diagnostically specific and global (ASI) psychiatric severity on outcome. More accurate identification of short of short- and long-range predictors of change in substance abuse status (remission and relapse) would provide information applicable to the design of better treatment strategies for drug abusers.